Planning of the September 11 attacks

In the United States on September 11, 2001 (9/11), 19 terrorists from al-Qaeda hijacked four airplanes and crashed them into important buildings.

American Airlines Flight 11 and United Airlines Flight 175 hit the World Trade Center. American Airlines Flight 77 hit the Pentagon. United Airlines Flight 93 was meant to hit a big government building, but it crashed in Pennsylvania instead.

The plans for these attacks started years before they happened. Someone in al-Qaeda first thought about bombing airplanes in 1995, but that plan was stopped. Later, the plan changed to crashing planes into famous buildings. After some time, the terrorists changed their plan again and finally carried out the attacks on September 11, 2001.

The terrorists who did this were part of a group in Germany. They later went to training camps in Afghanistan. Nineteen men from this group came to the United States in 2000 and 2001 and got ready to take over four airplanes. Sadly, many people lost their lives in these attacks. After that, many investigations began to learn more about what happened and who was responsible.

Background

Further information: Motives for the September 11 attacks

During the Soviet–Afghan War, the Soviet Union went into Afghanistan. Osama bin Laden left his home to help fight against them. He worked with others to support fighters called the Afghan mujahideen. After the Soviets left, bin Laden led a group called Maktab al-Khidamat. This group later became part of al-Qaeda.

Bin Laden had to leave Saudi Arabia in 1991 and moved to Sudan. Later, he had to leave Sudan and went back to Afghanistan. There, he was allowed to use the country as a base for his group. In 1996, bin Laden asked American troops to leave Saudi Arabia. In 1998, he told Muslims to fight against Americans.

In August 1998, al-Qaeda bombed two U.S. embassies in Kenya and Tanzania. They also tried to cause trouble at Los Angeles International Airport, but they were stopped before they could do much. Later, they bombed USS Cole in Yemen.

1990s–1996: Origins of the hijacking plan

In the early 1990s, a man named Khalid Sheikh Mohammed became an important leader in a group called al-Qaeda. He created a plan for attacks on airplanes, calling it "Bojinka." The plan was to destroy airplanes flying from Southeast Asia to the United States.

In 1993, some members of al-Qaeda, including Ramzi Yousef, damaged the World Trade Center in New York City. Later, Yousef and others tried to make bombs in his apartment in Manila. In 1995, a fire in Yousef’s apartment led police to find his laptop and bomb items. Yousef was captured and sent to the U.S. for prison.

1996–1999: Plan redesigns

In 1996, a man named Mohammed told a leader named bin Laden about a new idea. The idea was for members of a group to take over ten airplanes in the United States. Nine of these airplanes would crash into important buildings, like the World Trade Center, the U.S. Capitol, the Pentagon, and other tall buildings in different cities.

Later, in 1999, bin Laden agreed to a simpler version of the plan. They decided that if the airplanes could not reach their targets, the hijackers would crash them where they were. The targets chosen represented different parts of the United States, like its economy, military, and politics.

1990s–2000: Hamburg cell

Main article: Hamburg cell

In 1992, a man named Mohamed Atta from Egypt moved to Germany to study urban planning in Hamburg. He started going to a local mosque and became part of a group with strong religious beliefs. This group was called the Hamburg cell.

The Hamburg cell had twelve members, including Atta. Some came to Hamburg to study. They met and were influenced by others who had fought in wars. Over time, they became more interested in serious actions. In 1999, they met someone who invited them to join a larger group called al-Qaeda. This changed their plans, and they began working on a big idea.

Four of the members, including Atta, went to a training place to learn. They then returned to Germany and continued their work, often meeting in Atta's apartment to discuss their plans.

Hijackers and their collaborators

Further information: Hijackers in the September 11 attacks and 20th hijacker

On September 11, 2001, 19 members of al-Qaeda hijacked four planes in the United States. All 19 died when the planes crashed. Khalid Sheikh Mohammed helped the hijackers with travel and other needs.

Al-Qaeda's leaders chose the hijackers for their skills and experience. Some could speak English and had lived in Western countries. They prepared carefully for their actions.

American Airlines Flight 11 crashed into the first tower of the World Trade Center. The hijackers included Mohammed Atta and several others from Saudi Arabia.

United Airlines Flight 175 crashed into the second tower. The hijackers included Marwan al-Shehhi and others from the United Arab Emirates and Saudi Arabia.

American Airlines Flight 77 crashed into the Pentagon. All five hijackers were from Saudi Arabia, including Hani Hanjour, who was a trained pilot.

United Airlines Flight 93 crashed in Pennsylvania after the passengers tried to stop the hijackers. The plane did not reach its intended target. The hijackers included Ziad Jarrah from Lebanon and others from Saudi Arabia.

2000–2001: Hijackers', collaborators', and suspects' actions

2000

In 1999, messages from an al-Qaeda place in Yemen were found by the CIA. They talked about some al-Qaeda members, including Khalid al-Mihdhar and Nawaf al-Hazmi, meeting in Kuala Lumpur in January 2000. The meeting happened as planned, and the CIA took pictures of the people who arrived. After September 11, 2001, U.S. intelligence thought the meeting was to plan future attacks. Three of the people in the pictures were al-Mihdhar, al-Hazmi, and bin al-Shibh.

Al-Mihdhar and al-Hazmi arrived in Los Angeles from Bangkok on or around January 15. This was the first time any of the hijackers entered the U.S. They met Omar al-Bayoumi, a Saudi man who helped them move into an apartment in San Diego. They took flying lessons there but did not do well, so they became "muscle" hijackers instead of pilots. Some people thought al-Bayoumi might have helped with the plan, but he said it was a chance meeting. In 2002, the U.S. was looking into him, but he was never charged.

Mohamed Atta, Ramzi bin al-Shibh, and Ziad Jarrah were in Afghanistan in January 2000. Later in January, Marwan al-Shehhi and Atta hid their time in Afghanistan by reporting their passports as stolen in Germany. Jarrah did the same in February. In March, Atta emailed a flight school in Florida about their services. He sent many similar emails to other schools. On May 18, Atta got a U.S. visa. On the 25th, Jarrah did the same. Al-Shehhi arrived in the U.S. on the 29th. On June 3, Atta arrived in the U.S. Around early June, he and al-Shehhi went to a flight school in Oklahoma. Bin al-Shibh tried to get a U.S. visa four times from June to October but was denied because he was from Yemen. Zakariya Essabar, a Moroccan, was also denied.

Al-Shehhi, Atta, and Jarrah went to a flight school in Venice, Florida, and visited Huffman Aviation. They said they were not happy with another school in the area. From around June to September 2000, al-Shehhi got several wire transfers from someone in the UAE. In the same period, bin al-Shibh sent money to Atta and al-Shehhi in Florida. Between June 2000 and September 11, Atta looked into starting a crop dusting company; another hijacker, Zacarias Moussaoui, did the same around June 2001.

Around October, Moussaoui got letters from a Malaysian company saying he was hired as a marketing consultant in the U.S., U.K., and Europe.

In Ohio, around November 25, Atta bought videos of Boeing 747 and Boeing 757 flight decks from a store. Later in December, he bought videos of Boeing 757 and Airbus A320 models. On December 21, he and al-Shehhi got their pilot's licenses from Huffman Aviation.

Bin al-Shibh went from Hamburg to London around December 2 to 9. On December 8, Hani Hanjour entered the U.S. for the last time in San Diego. He later went to Arizona to practice flying. Around December 9, Moussaoui flew from London to Pakistan.

Early-to-mid 2001

Moussaoui had flight training at a school in Phoenix, Arizona, from January to March 2001. Around February 1, Atta had a test flight around Decatur, Georgia, and al-Shehhi had one around February 15.

Moussaoui flew back to London around February 7, then to Chicago around February 23, and to Oklahoma City later that day. Three days later, he went to Norman and opened a bank account, putting about $32,000 into it. He attended flight training at the Airman Flight School from February to May but stopped early.

In February, someone with Abdulaziz al-Omari's name visited the Philippines twice.

Around March 19, Nawaf al-Hazmi bought flight deck videos of Boeing 747 models at the Ohio Pilot Store. He was known to be in Oklahoma around April 1.

Jarrah and Atta got their Florida driver's licenses on May 2.

On May 19, al-Suqami and Waleed al-Shehri flew from Fort Lauderdale, Florida, to Freeport, Bahamas, but they lacked proper documents and returned the same day. They rented a car and went back to Florida.

Wail al-Shehri arrived in the U.S. in June. On June 8, Ahmed al-Haznawi arrived in Florida and moved in with Jarrah. Later, Jarrah rented a new apartment in Lauderdale-by-the-Sea, Florida, and al-Haznawi moved with him.

On June 29, al-Omari and Salem al-Hazmi arrived in the U.S. in New York City after leaving Dubai. Salem had a tourist visa. They were probably picked up by Nawaf al-Hazmi, as there was a traffic accident involving Nawaf on the George Washington Bridge on June 30. Al-Omari likely stayed with other hijackers in Paterson, New Jersey, before moving to Vero Beach, Florida, with his wife and three children.

In summer 2001, several hijackers opened bank accounts at SunTrust in Florida. In June, at a bank in Dubai, conspirator Mustafa al-Hawsawi opened a checking account. In July, al-Hawsawi got power of attorney over Banihammad's accounts and picked up ATM and Visa cards for him, which were sent to Florida.

Around June 20, Moussaoui bought flight deck videos of Boeing 747 models at the Ohio Pilot Store. Around July 10 or 11, Moussaoui paid for simulator courses of commercial flights at a school in Phoenix. From July 29 to August 2, Moussaoui used payphones to call numbers in Düsseldorf. In Hamburg around July 30 to 31, bin al-Shibh, using a fake name, got about $15,000 USD from someone in the UAE.

In July, Waleed al-Shehri flew on a commercial plane from Florida to San Francisco and stayed in Las Vegas for a night on the way back. The reason for the trip is unknown. Atta bought a knife in Zurich around July 8.

Before the attacks, Jarrah's uncle told the Lebanese government and the American embassy that something dangerous was happening with Ziad, who was becoming more extreme. Nobody paid attention. Atta complained to bin al-Shibh about having trouble reaching Jarrah. Jarrah left the plan at one point but came back; he might have done this twice. In July, Atta met bin al-Shibh in Spain to discuss the plan and decide the targets. Bin al-Shibh told Atta that bin Laden wanted the attacks to happen soon. On July 25, Jarrah flew from the U.S. to Germany and met with bin al-Shibh, who convinced him to go through with the operation.

August 2001

Around August 1 to 3, bin al-Shibh sent about $14,000 USD to Moussaoui in Oklahoma. On August 3, Moussaoui bought two knives in Oklahoma City. He was driven to Minnesota around August 9 and paid about $6,300 for training at a flight school in Minneapolis on August 10. From August 13 to 16, he trained on a Boeing 747 simulator.

Jarrah may have returned to the U.S. on August 5, though some sources say he took his pilot's test in the U.S. on August 2. Around August 17, Jarrah had a test flight in Fort Lauderdale. Around August 22, he bought schematics of a Boeing 747 cockpit and various GPS equipment, including an antenna.

Ahmed Omar Saeed Sheikh, described by the U.S. as a key figure in funding for al-Qaeda, used a fake name to send $100,000 USD to Atta. Atta then gave the money to the other hijackers in Florida. About three weeks before the attacks, the targets were assigned to four teams.

The hijackers bought their flight tickets in August and early September. On August 24, al-Mihdhar and Moqed tried to buy tickets online from American Airlines but had trouble and gave up. On August 27, Nawaf and Salem al-Hazmi bought tickets for Flight 77. On August 28, Wail and Waleed bought tickets for Flight 11, and Atta bought tickets for himself and al-Omari on the same flight. On August 29, Banihammad and Hamza al-Ghamdi bought tickets for Flight 175. The FBI said Hamza also bought a ticket for "Flight 7950" from Los Angeles to San Francisco, but they did not say when the flight was supposed to be. On August 31, Moqed and Hanjour went to a travel agency in Totowa, New Jersey, and asked for two tickets for a flight on September 11. Moqed, speaking for Hanjour, decided to only buy a ticket for Hanjour on Flight 77.

Over a few days in late August and early September, six of the hijackers stayed in Laurel, Maryland, at two motels; it is unknown if this was to watch the NSA's headquarters, which were a few miles away.

Reasoning for attacking on September 11

It is not known why September 11 was chosen as the attack date. Al-Qaeda might have used numerology in choosing it. Before the attacks, the group's internal name for the plan was "Operation Holy Tuesday"; September 11, 2001, was a Tuesday. They might have also wanted revenge for September 11, 1683, when the Ottoman Empire's expansion into Europe ended at the Battle of Vienna. They could have also referenced September 11, 1973, when the U.S. helped overthrow the Chilean president Salvador Allende in a coup.

Early September 2001

In early September, Jarrah asked his father for money for flight training. His father gave him $2000 USD, which investigators think was for tickets for Flight 93. Wail and Waleed called American Airlines on September 3 to change their seat assignments for Flight 11, choosing seats in first class on the other side of the aircraft for a better view of the cockpit. On September 5, al-Mihdhar and Moqed went to the American Airlines counter at BWI Airport in Baltimore and bought tickets for Flight 77.

Seating manifests of the 9/11 flights

American Airlines Flight 11

United Airlines Flight 175

American Airlines Flight 77

United Airlines Flight 93

In the week before September 11, al-Hawsawi got extra money from at least four hijackers. The FBI thought this was because they did not want to "die as thieves". Banihammad's SunTrust account sent about $8,055 USD to one of his Dubai accounts that al-Hawsawi could access. Al-Hawsawi then got $2,860 and $5,000 from Atta, $5,400 from al-Shehhi, and $5,000 from Waleed al-Shehri. He also got a Fed-Ex package of unknown contents from Atta.

Jarrah returned to Florida by September 7. On that day, he and the three other Flight 93 hijackers—al-Nami, al-Haznawi, and Saeed al-Ghamdi—flew from Fort Lauderdale to Newark International Airport.

Morning of September 11, 2001

Main article: September 11 attacks

On the morning of September 11, 2001, a group of people made phone calls to get ready for their plans. They went to different airports across the United States. They were all allowed to get on their flights, even though some had set off security alarms.

The four airplanes took off between 7:59 and 8:42 a.m. Soon after, the people on the planes took control of the airplanes. They hurt the pilots and crew members. Then they steered the planes toward important buildings in New York, Virginia, and Washington, D.C. There were four crashes that morning: at 8:46 a.m., one plane hit the first tower of the World Trade Center; at 9:03 a.m., another hit the second tower; at 9:37 a.m., a third plane hit the Pentagon; and at 10:03 a.m., the last plane crashed in Pennsylvania.

Pre-September 11 investigations

Main article: September 11 intelligence before the attacks

Before September 11, 2001, many people were working to stop dangerous plans. In Germany, some people were watched because they were linked to a group of terrorists. This helped find the names of two men who later took part in the attack. But the people in charge of safety didn’t fully understand what was happening.

In 1996, American leaders started watching a man named bin Laden because he talked about hurting the United States. Over time, they received many warnings that something bad might happen, like hijackings. However, different groups didn’t share their information well, so the full danger wasn’t clear. Important messages, like one written in July 2001 warning about people training to fly planes, weren’t seen by the top leaders until after the attacks. Even a special report to the president in August 2001 mentioned that bin Laden wanted to attack the U.S., but many details were still unknown.

Post-September 11 investigations

Further information: Aftermath of the September 11 attacks

On September 11, 2001, U.S. intelligence learned that al-Qaeda was behind the attacks. By the end of the day, officials had collected strong evidence. The FBI started one of the biggest investigations ever. They interviewed many people and looked at lots of documents. They worked with intelligence agencies around the world to gather more information.

Investigations also studied how the attacks were planned and paid for. A special commission was created to look at what happened and to suggest ways to stop future attacks. This commission found that problems with sharing information stopped the government from fully understanding the danger before the attacks. They thought the plot cost between $400,000 and $500,000.

Into Saudi involvement

Main article: Alleged Saudi role in the September 11 attacks

Some investigators wondered if Saudi Arabia may have helped the planners of the attacks, but the official report found no proof that any foreign government gave money. Saudi Arabia denied these claims. There were reports of possible links between some of the attackers and people connected to Saudi officials, but this is still being talked about.

Into Pakistani involvement

Further information: Pakistan and state-sponsored terrorism

There were also questions about whether officials in Pakistan may have known about or helped some of the attackers. These claims led to talks between U.S. and Pakistani leaders, but the whole story is still complicated and being discussed.

Into hijackers' Maine and Nevada trips

Some people said they saw the attackers in Portland, Maine, before the attacks, but investigations did not find proof of a local group there. The reasons why some attackers visited Las Vegas before September 11 are still unknown.

Conspirators' and suspects' aftermaths

Conspirators who were convicted or indefinitely detained

After the September 11 attacks, the United States created special prisons around the world and opened places like Guantanamo Bay detention camp to hold people they thought were involved in the attacks.

Khalid Sheikh Mohammed and Ramzi bin al-Shibh hid in Pakistan after the attacks. They admitted to taking part in the plans. Bin al-Shibh was captured and held for years before being moved to Guantanamo.

Mohammed was also captured and held for years. Mustafa al-Hawsawi and Walid bin Attash were also detained at Guantanamo.

Conspirators who were not convicted

From 2001 to 2011, the United States searched for Osama bin Laden, who was behind the attacks. In 2011, U.S. forces found and killed him in Pakistan.

Abdelghani Mzoudi was arrested in Germany but later freed due to lack of evidence. Mamoun Darkazanli was not arrested for being in the group but faced charges in Spain for other reasons.

Said Bahaji, Zakariya Essabar, and Naamen Meziche were thought to have moved to Pakistan or Afghanistan after the attacks. Their whereabouts remain unknown or unconfirmed.

Suspects

Ammar al-Baluchi was captured and held for years. Mohamedou Ould Slahi was also captured and held but was later freed when it was found that some claims about him were not true.